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Browsing by Author "Mukhopadhyay, Sudarsan"

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  • Effect of pomegranate powder on the heat inactivation of Escherichia coli O104: H4 in ground chicken
    Publication . Juneja, Vijay K.; Cadavez, Vasco; Gonzales-Barron, Ursula; Mukhopadhyay, Sudarsan; Friedman, Mendel
    Health concerns have led to a search for natural plant-based antimicrobials. Ellagic acid has been shown to have antimicrobial activity against foodborne pathogens. The objective of this study was to assess the effect of a high-ellagic acid commercial pomegranate on the heat resistance of Escherichia coli O104:H4 in ground chicken. A full 2 4 factorial design was used, consisting of temperature treatment with four levels (55.0, 57.5, 60.0, and 62.5 °C) and pomegranate with four levels (0.0, 1.0, 2.0, and 3.0 wt/wt. % containing 70% ellagic acid). Experiments were conducted twice, providing a total of 32 survival curves. A three-parameter Weibull primary model was used to describe survival kinetics. Secondary models were then developed to estimate the shape parameter ß (i.e., curvature representing susceptibility of cells to stress), scale parameter ? (i.e., time to reach the first decimal reduction) and the 5.0-log lethality time t 5.0 (i.e., time to reach a 5.0-log reduction), all as polynomial functions of temperature and pomegranate powder concentration. The positive effect of pomegranate concentration on both ß and ? demonstrated that the phenolic-rich pomegranate powder causes E. coli O104:H4 cells to become more susceptible to heat, increasing the steepness and concavity of the isothermal survival curves. It was estimated that the 5.0-log reduction time would reach a minimum at a pomegranate powder concentration of 1%, producing a 50% decrease in lethality time, in comparison to that without added pomegranate powder. Nonetheless, a mixed-effect omnibus regression further confirmed that the greatest difference in the thermal resistance of E. coli O104:H4 happened between tests with and without pomegranate powder. In fact, adding more than 1.0% pomegranate powder, at a constant temperature, resulted only in a marginal decrease in thermal resistance. Meat processors can use the model to design lethality treatments in order to achieve specific reductions of E. coli O104:H4 in ground chicken.
    2016Journal article Open access Show more
  • Modelling the effect of pH, Sodium chloride and sodium pyrophosphate on the thermal resistance of Escherichia coli O157: H7 in ground beef
    Publication . Juneja, Vijay K.; Cadavez, Vasco; Gonzales-Barron, Ursula; Mukhopadhyay, Sudarsan
    The objective of this study was to assess the combined effects of temperature, pH, sodium chloride (NaCl), and sodium pyrophosphate (SPP) on the heat resistance of Escherichia coli O157:H7 in minced beef meat. A fractional factorial design consisted of four internal temperatures (55.0, 57.5, 60.0 and 62.5. °C), five concentrations of NaCl (0.0, 1.5, 3.0, 4.5 and 6.0. wt/wt.%) and SPP (0.0, 0.1, 0.15, 0.2 and 0.3. wt/wt.%), and five levels of pH (4.0, 5.0, 6.0, 7.0 and 8.0). The 38 variable combinations were replicated twice to provide a total of 76 survivor curves, which were modelled by a modified three-parameter Weibull function as primary model. The polynomial secondary models, developed to estimate the time to achieve a 3-log and a 5-log reduction, enabled the estimation of critical pH, NaCl and SPP concentrations, which are values at which the thermo-tolerance of E. coli O157:H7 reaches it maximum. The addition up to a certain critical concentration of NaCl (~. 2.7-4.7%) or SPP (~. 0.16%) acts independently to increase the heat resistance of E. coli O157:H7. Beyond such critical concentrations, the thermo-resistance of E. coli O157:H7 will progressively diminish. A similar pattern was found for pH with a critical value between 6.0 and 6.7, depending upon temperature and NaCl concentration. A mixed-effects omnibus regression model further revealed that the acidity of the matrix and NaCl concentration had a greater impact on the inactivation kinetics of E. coli O157:H7 in minced beef than SPP, and both are responsible for the concavity/convexity of the curves. When pH, SPP or NaCl concentration is far above or below from its critical value, the temperatures needed to reduce E. coli O157:H7 up to a certain log level are much lower than those required when any other environmental condition is at its critical value. Meat processors can use the model to design lethality treatments in order to achieve specific log reductions of E. coli O157:H7 in ready-to-eat beef products.
    2015Journal article Open access Show more